The present invention relates to a tape guide arrangement for a helical scan magnetic recording and playback apparatus which includes a stationary lower drum and a rotatable upper drum and, more particularly, to a tape guide arrangement including a stationary lower drum which is provided with a unique tape guide for smoothly guiding a magnetic tape.
In a recording and playback apparatus of the kind described, a magnetic tape is generally transported helically wrapping around a guide drum over a predetermined angular range. To implement such a manner of tape transport, a stationary lower drum of a guide drum assembly is usually provided with a tape transport guide adapted to guide a magnetic tape helically along a predetermined path.
In such a prior art tape guide arrangement, the tape transport guide is formed in part of the outer periphery of the lower drum and made up of a shoulder to be engaged by the lower edge of a running magnetic tape and a tape sliding surface to be engaged by one surface of the tape. The problem encountered with this kind of tape transport guide is that the area over which the tape surface contacts the tape sliding surface of the lower drum and, therefore, friction developing therebetween is relatively large, liable to develop unstable transport of the tape and make the tape and guide drum assembly easy to be worn out or damaged. An attempt heretofore made to solve such a problem consists in joining the shoulder and the tape sliding surface to each other by an intermediary curved surface to reduce the friction due to contact, as disclosed in Japanese Patent Laid-Open Publication No. 58-45654/1983, for example. This approach, however, brings about another problem that upon contact of the lower edge of a magnetic tape in transport with the curved surface the level, or height, of the tape is apt to fluctuate in height and fail to be maintained at a predetermined position.